Regarding the associations of KIT Exon 11 mutation type and best overall response (BOR) in metastatic GIST patients treated with first-line imatinib, patients with deletion or delins regardless of codon regions had a significantly better CR rate (557/558: 40%; other codons: 37.5%) compared to the patients with other PVs (Dup, Ins or SNV) (5.3%) (p = 0.006). This evidence concerns the gene KIT and gastrointestinal stromal tumor.